Today at Coldwater Gardens, I learned why and how to prune tomatoes:
WHY: Pruning tomato plants will help increase the efficiency of photosynthesis–leading to well fed, large fruits, produced consistently throughout the growing season.
A (indeterminate) tomato plant that is not pruned will begin producing as much as 3 weeks later than a well pruned plant; and although it may produce more tomatoes at once, the fruits will be quite a bit smaller (than those of a pruned plant).
If left unpruned, an indeterminate tomato plant will develop as many as 10 stems–each of which will produce fruit.
The fruits feed off of the sugar produced by the plant during photosynthesis; the more fruits there are, the less sugar/food there is to go around, and so the tomatoes will be smaller.
To ensure bigger fruits throughout the season, many gardeners choose to keep their tomato plants pruned to one or two stems; this also makes the plant easier to stake upright and manage.
But what part of the plant do you remove? And HOW?
Remove “suckers” before they become stems. —Suckers are shoots that develop between the main stem and the leaves of the main stem; if left untouched they will continue to grow until they become a stem all their own and begin producing fruit.
If caught early, when still small, the entire sucker should be removed by hand or with a sharp, clean blade; this is known as “simple pruning.”
However, if the sucker is large before you notice it (a few inches long) it’s best to remove just the tip and leave one or two leaves (otherwise the plant could be shocked by losing such a large piece); this is known as “Missouri pruning. *Note that the tip of the sucker will grow back, and will need to be continually removed.